为什么double.Parse（“0.05”）返回5.0？

Question

I am reading a value from my App.config; which is:

 <add key="someValue" value="0.05"/>

And I try to convert it to double by doing:

 var d = double.Parse(ConfigurationManager.AppSettings["someValue"]);

And I obtain 5.0 insteads of 0.05.

Can you advice? What do I do wrong and how should I parse this?

Answer 1

That's for your culture settings, Test the same but with a comma instead a point and you will see that work's

var d = double.Parse("0,05");

To fixed this problem you could used the follow overload of the parse function

var d = double.Parse(ConfigurationManager.AppSettings["someValue"], CultureInfo.InvariantCulture);

Answer 2

Maybe the problem is in the culture settings. There could be many issues with them, such as comma as digital separator. When you're working with non-cultured values, such as config files, you should explicitly specify that you need InvariantCulture. Try

var d = double.Parse(ConfigurationManager.AppSettings["someValue"],
                     CultureInfo.InvariantCulture);

Answer 3

This code:

var nfi = new NumberFormatInfo {
    NumberGroupSeparator = ".",
    NumberDecimalSeparator = ","
};
Console.WriteLine(double.Parse("0.05", nfi));

prints 5 as well, so the problem is in your culture settings.

Try

var d = double.Parse(
    ConfigurationManager.AppSettings["someValue"], 
    CultureInfo.InvariantCulture);

Answer 4

Always pass your culture info when using double.Parse. Here in Belgium, it's "0,05".

Answer 5

It's because of culture settings. Please ensure "." is a delimiter in your current culture.